using System;

namespace _0445
{
    class Program
    {
        static void Main(string[] args)
        {
            var _ = Console.ReadLine().Split();
            var a = double.Parse(_[0]);
            var b = double.Parse(_[1]);

            var x = 50 * a;
            var y = x / Math.Floor(0.2 * b + 0.8);

            Console.WriteLine(x + y);
        }
    }
}